In a wireless communication networks, there are communication nodes, for example base stations. The base stations normally comprise sector-covering antenna arrangements. Such an antenna arrangement comprises a number of antenna ports corresponding to branches for uplink and downlink, where downlink denotes transmission, TX, from the base station to other nodes such as mobile terminals, and uplink denotes reception, RX, to the base station from other nodes such as mobile terminals. A downlink branch is thus a TX branch and an uplink branch is thus an RX branch.
Normally a typical system configuration may comprise two TX branches in the form of transmission channels and two RX branches in the form of reception channels, but system configurations with two TX branches and four RX branches are more attractive since the additional two RX branches provide large uplink improvements for a relatively small cost and volume increase.
Even more attractive are system configurations with four TX branches and four RX branches, enabling four-layer MIMO (Multiple Input Multiple Output) transmission. Furthermore, some operators have three different frequency bands, for example the frequency bands B1, B3 and B7 in the 1710-2690 MHz frequency interval. Four-layer MIMO implies that a four port antenna such as a dual column dual polarized antenna system is required for each frequency band, which in turn means that a complex antenna system with twelve antenna ports is required to support 4TX/4RX functionality on all three bands.
There is thus a need for an uncomplicated 4TX/4RX triple band antenna arrangement in a node comprising an efficiently used antenna aperture.